Hartlett knocked out Gold Coast's Seb Tape with a brutal bump and also suffered an apparent serious shoulder injury in Port's 16.17 (113) to 14.12 (96) victory.
The key Power on-baller was helped from AAMI Stadium in the final term clutching his left shoulder - the same body joint which knocked Tape out in a second quarter shepherd.
Hartlett's crunching bump will be scrutinised by the match review panel after Port moved closer to a return to the finals by banking their 12th win of the season.
The Power remain eighth, two wins ahead of ninth-placed Carlton with two games remaining before finals.
Port were nine points down at three quarter-time but young gun Chad Wingard booted two goals in 90 seconds to take back the lead.
The Power kicked six goals to two in the last term to over-run a tiring Suns outfit but Hartlett's season could be over - through injury, suspension, or both.
Hartlett caught an unsuspecting Tape with a shepherd which instantly knocked the Gold Coast player out in the 14th minute of the second term.
The Port star indicated there was a clash of heads but replays showed head-high contact with his shoulder.
Hartlett's game ended when he hurt the same shoulder when tackled by two Suns players. The 23-year-old has already had shoulders reconstructed twice.
The spotlight on Hartlett came after Port produced their highest-scoring opening quarter of the season, kicking 7.5 to 3.5.
The Power then seemingly went out as Gold Coast rallied, the visitors taking the lead in the third term of a match watched in part by campaigning Prime Minister Kevin Rudd.
But the Suns, who were inspired by a brilliant 28-possession, three-goal game by Harley Bennell, were headed early in the last when the 20-year-old Wingard confirmed his growing status as a player for a crisis.
Wingard booted two rapid last term goals before captain Travis Boak later capped his best-afield 35-disposal display by sealing the result with his third goal.
Port's Kane Cornes shaded Suns superstar Gary Ablett, whose 22 disposals had limited impact, while Gold Coast forward Andrew Boston potted three goals.
PORT ADELAIDE 7.5 8.9 10.13 16.17 (113)
GOLD COAST SUNS 3.5 6.8 12.10 14.12 (96)
Goals: Port Adelaide - Schulz, Boak 3; Heath, Wingard, Westhoff 2; Moore, Young, Brad Ebert, Cornes. Gold Coast Suns - Boston, Bennell 3; Stanley 2; Dixon, Gorringe, J Hall, Hutchins, O'Meara, Sumner.
Best: Port Adelaide - Boak, Broadbent, Cornes, Monfries, Gray, Brad Ebert, Westhoff. Gold Coast Suns - Bennell, Stanley, Prestia, Boston, Gorringe, Ablett.
Umpires: Simon Meredith, Jeff Dalgleish, Matthew Leppard.
Official Crowd: 18,703 at AAMI Stadium.